This invention relates to novel tetrahydrocarbazole acetic acid derivatives possessing lipoxygenase inhibitory and/or cyclooxygenase inhibitory activity which are useful as anti-inflammatory and antiallergic agents. For instance, they exhibit analgesic and anti-inflammatory activity at dose levels which do not elicit undesirable side effects. The foregoing combination of attributes render the compounds of this invention useful for the treatment of inflammatory conditions and of pain and allergy.
It is known that arachidonic acid (AA) is metabolized in mammals by two distinct pathways. The metabolism of arachidonic acid by cyclooxygenase enzymes results in the production of prostaglandins and thromboxanes. The physiological activity of the prostaglandins has already been amply elucidated in recent years. The other pathway of AA metabolism involves lipoxygenase enzymes and results in the production of a number of oxidative products called leukotrienes. The latter are designated by the LT nomenclature system, and the most significant products of the lipoxygenase metabolic pathway are the leukotrienes B.sub.4, C.sub.4, D.sub.4 and E.sub.4. The substance denominated slow-reacting substance of anaphylaxis (SRS-A) has been shown to consist of a mixture of sulfidopeptide leukotrienes, C.sub.4, D.sub.4 and E.sub.4 [see Back et al, J. Immun., 215, 115-118 (1980); Biochem. Biophys. Res. Commun. 93, 1121-1126 (1980)].
The significance of these leukotrienes is that a great deal of evidence has been accumulated showing that leukotrienes participate in inflammatory reactions, exhibit chemotactic activities, stimulate lysosomal enzyme release and act as important factors in the immediate hypersensitivity reaction. It has been shown that LTC.sub.4 and LTD.sub.4 are potent bronchoconstrictors of the human bronchi [see Dahlen et al, Nature, 288, 484-486 (1980) and Piper, Int. Arch. Appl. Immunol., 76, suppl. 1, 43 (1985)] which stimulate the release of mucus from airways in vitro [Marom et al, Am. Rev. Resp. Dis., 126, 449 (1982)], are potent vasodilators in skin [see Bisgaard et al, Prostaglandins, 23, 797 (1982)], and produce a wheal and flare response [Camp et al, Br. J. Pharmacol., 80, 497 (1983)]. The nonpeptide leukotriene, LTB.sub.4, is a powerful chemotactic factor for leukocytes [see A. W. Ford-Hutchinson, J. Roy. Soc. Med., 74, 831-833 (1981)], which stimulates cell accumulation and affects vascular smooth muscle [see Bray, Br. Med. Bull., 39, 249 (1983)]. The activity of leukotrienes as mediators of inflammation and hypersensitivity is extensively reviewed in Bailey and Casey, Ann. Reports Med. Chem., 17, 203-217 (1982) and in Bray, Agents and Actions, 19, 87 (1986).
Accordingly, the biological activity of the leukotrienes and SRS-A's, and of lipoxygenase as the enzyme leading to the metabolism of AA to leukotrienes, indicates that a rational approach to drug therapy to prevent, remove, or ameliorate the symptoms of allergies, anaphylaxis, asthma and inflammation must focus on blocking the release of mediators of these conditions. Thus, compounds which control the biosynthesis of the leukotrienes and SRS-A's by inhibiting lipoxygenase, are considered to be of value in treating such conditions as allergic bronchial asthma, allergic rhinitis, as well as in other immediate hypersensitivity reactions.